Psi (Cyrillic)
Psi is a letter in the early Cyrillic alphabet, derived from the Greek letter psi. It represents the sound /ps/, as in English naps. According to the school rules developed in the 16th and the 17th centuries, such as Meletius Smotrytsky's grammar book, it was intended for use in words of Greek origin, but it was occasionally used for writing native words as well like Ukrainian . It was used especially in words relating to the Eastern Orthodox Church, as can be seen in its continuing use in Church Slavonic.
Psi was eliminated from the Russian orthography along with ksi, omega, and yus in the Civil Script of 1708, and it has also been dropped from other secular languages. It continues to be used in Church Slavonic.
